Spatial grid correction for short-term numerical simulation results of carbon dioxide dissolution in saline aquifers

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

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Experiment and simulation about the effect of wear-ring abrasion on the performance of a marine centrifugal pump

Advances in Mechanical Engineering ◽

10.1177/1687814021998115 ◽

2021 ◽

Vol 13 (2) ◽

pp. 168781402199811

Author(s):

Wu Xianfang ◽

Du Xinlai ◽

Tan Minggao ◽

Liu Houlin

Keyword(s):

Numerical Simulation ◽

Centrifugal Pump ◽

Pressure Pulsation ◽

Vibration Velocity ◽

Test Results ◽

Obvious Effect ◽

Performance Change ◽

Pump Test ◽

Simulation Results ◽

Axis Passing

The wear-ring abrasion can cause performance degradation of the marine centrifugal pump. In order to study the effect of front and back wear-ring clearance on a pump, test and numerical simulation were used to investigate the performance change of a pump. The test results show that the head and efficiency of pump decrease by 3.56% and 9.62% respectively at 1.0 Qd due to the wear-ring abrasion. Under 1.0 Qd, with the increase of the front wear-ring the vibration velocity at pump foot increases from 0.4 mm/s to 1.0 mm/s. The axis passing frequency (APF) at the measuring points increases significantly and there appears new characteristic frequency of 3APF and 4APF. The numerical simulation results show that the front wear-ring abrasion affects the flow at the inlet of the front chamber of the pump and impeller passage. And the back wear-ring abrasion has obvious effect on the flow in the back chamber of the pump and impeller passage, while the multi-malfunction of the front wear-ring abrasion and back wear-ring abrasion has the most obvious effect on the flow velocity and flow stability inside pump. The pressure pulsation at Blade Passing Frequency (BPF) of the three schemes all decrease with the increase of the clearance.

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Development of Depth-Limited Wave Boundary Layers over a Smooth Bottom

Journal of Marine Science and Engineering ◽

10.3390/jmse9010027 ◽

2020 ◽

Vol 9 (1) ◽

pp. 27

Author(s):

Hitoshi Tanaka ◽

Nguyen Xuan Tinh ◽

Xiping Yu ◽

Guangwei Liu

Keyword(s):

Numerical Simulation ◽

Boundary Layer ◽

Boundary Layers ◽

Wave Motion ◽

Numerical Study ◽

Experiment Data ◽

Tidal Motion ◽

Long Period ◽

Simulation Results ◽

Wave Boundary

A theoretical and numerical study is carried out to investigate the transformation of the wave boundary layer from non-depth-limited (wave-like boundary layer) to depth-limited one (current-like boundary layer) over a smooth bottom. A long period of wave motion is not sufficient to induce depth-limited properties, although it has simply been assumed in various situations under long waves, such as tsunami and tidal currents. Four criteria are obtained theoretically for recognizing the inception of the depth-limited condition under waves. To validate the theoretical criteria, numerical simulation results using a turbulence model as well as laboratory experiment data are employed. In addition, typical field situations induced by tidal motion and tsunami are discussed to show the usefulness of the proposed criteria.

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Numerical Simulation of the Performance of an Axial Compressor Operating With Supercritical Carbon Dioxide

Volume 8: Computational Fluid Dynamics (CFD); Nuclear Education and Public Acceptance ◽

10.1115/icone26-81573 ◽

2018 ◽

Author(s):

Jinlan Gou ◽

Wei Wang ◽

Can Ma ◽

Yong Li ◽

Yuansheng Lin ◽

...

Keyword(s):

Carbon Dioxide ◽

Numerical Simulation ◽

Supercritical Carbon Dioxide ◽

Critical Point ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Axial Compressor ◽

Brayton Cycle ◽

Supercritical Carbon

Using supercritical carbon dioxide (SCO2) as the working fluid of a closed Brayton cycle gas turbine is widely recognized nowadays, because of its compact layout and high efficiency for modest turbine inlet temperature. It is an attractive option for geothermal, nuclear and solar energy conversion. Compressor is one of the key components for the supercritical carbon dioxide Brayton cycle. With established or developing small power supercritical carbon dioxide test loop, centrifugal compressor with small mass flow rate is mainly investigated and manufactured in the literature; however, nuclear energy conversion contains more power, and axial compressor is preferred to provide SCO2 compression with larger mass flow rate which is less studied in the literature. The performance of the axial supercritical carbon dioxide compressor is investigated in the current work. An axial supercritical carbon dioxide compressor with mass flow rate of 1000kg/s is designed. The thermodynamic region of the carbon dioxide is slightly above the vapor-liquid critical point with inlet total temperature 310K and total pressure 9MPa. Numerical simulation is then conducted to assess this axial compressor with look-up table adopted to handle the nonlinear variation property of supercritical carbon dioxide near the critical point. The results show that the performance of the design point of the designed axial compressor matches the primary target. Small corner separation occurs near the hub, and the flow motion of the tip leakage fluid is similar with the well-studied air compressor. Violent property variation near the critical point creates troubles for convergence near the stall condition, and the stall mechanism predictions are more difficult for the axial supercritical carbon dioxide compressor.

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